The invention relates to a retaining clamp for securing objects, in particular gas storage cylinders for airbags.
In order to secure objects, in particular cylindrical gas storage cylinders for airbags, the invention makes use of a retaining clamp which preferably has an encircling clamping ring designed as a sheet-metal punched part. Arranged on the clamping ring are a clamping means and a securing means, of which the former serves to securely clamp the clamping ring around the object while the latter serves to secure the retaining clamp and the object fixed by the latter in a clamping manner. In the case of securing gas storage cylinders for motor vehicle airbags, in particular side airbags, the retaining clamp is secured on a suitable vehicle part, for example on the chassis or on the door construction, by means of the securing means, in particular a press-in screw.
The arrangement is implemented in such a manner that the clamping ring of the retaining clamp encircles the object in the manner of a hose band clip, the encircling leading, after the object is securely clamped, to radial forces which fix the object with respect to the clamping ring and therefore with respect to the securing means. In order to produce a clamping force of sufficient magnitude between the clamping ring of the retaining clamp and the object and thereby to improve the holding effect, according to the invention a roughening is formed, at least in some regions, on at least one contact surface with which the retaining clamp bears against the object to be held. This roughening increases the coefficient of static friction between the contact surface and that surface of the object which bears against the contact surface, which makes it possible to more securely retain the object. This is important in particular in vehicle construction, since, if there is an accident-induced deformation of the vehicle, the gas storage cylinder, which may constitute the object to be held, has to be securely fixed in order to ensure correct activation of an associated airbag.
In a preferred refinement of the invention, provision is made for the roughening to have a surface roughness of at least approximately 1 μm. The roughening can be produced, for example, by the contact surface being machined by sandblasting using a sharp-edged, particulate material, the hardness of which is greater than the hardness of the clamping rings, so that the particles, when they strike against the contact surface, cause it to be deformed. As an alternative, the roughening may also be brought about by stamping the contact surface with a suitable stamping tool, either during punching of the retaining clamp, which is preferably designed as a sheet-metal part, or by using a metal sheet which has already been provided during the rolling process with a rough surface.
According to a further preferred refinement of the invention, the clamping ring has at least one stiffening bead which is surrounded by a contact surface and is pressed outward away from the surface of the object. Stiffening beads of this type make it possible, firstly, to reinforce the clamping or retaining force applied by the clamping ring on the object and, secondly, as a consequence of the clamping ring being stiffer, to counteract a deformation caused by external forces, for example accident-induced forces. The reinforcing beads preferably have an elongate shape with a longitudinal axis which extends in the circumferential direction of the clamping ring, and can expediently extend in each case over a circumferential angle of 60 to 120° on opposite sides of the object.
As an alternative or in addition, the clamping ring can have at least one convexity, i.e. a cross-sectionally arcuate stamping of the clamping ring with an apex line which is formed transversely with respect to the peripheral or circumferential direction thereof and below which the clamping ring does not bear against the surface of the object.
A further preferred refinement and/or variant of the invention makes provision for the securing of the retaining clamp to take place by means of a clamping securing bolt, which is preferably designed as a press-in screw, extends through an opening of the clamping ring, has a head lying in the interior of the clamping ring and a stem which protrudes outward through the opening, a rotation of the clamping securing bolt with respect to the clamping ring being prevented by the head having at least one rotation-preventing edge which lies at a short distance opposite part of the inside of the clamping ring.
The head of the clamping securing bolt preferably has a multi-edged contour and is expediently provided on diametrically opposite sides with two mutually parallel rotation-preventing edges which are arranged on both sides of a part of the inside of the clamping ring that serves as a seat for the lower side of the head, and lie there at a short distance opposite two sections of the clamping ring that are adjacent to the seat and are bent inward. The best is for the head to have an outline in the form of a square or other regular polygon with parallel sides, so that it can be aligned with respect to the seat in any desired rotational position of two or more rotational positions, in which two side surfaces of the head that serve as rotation-preventing edges lie opposite those sections of the clamping ring which are adjacent to the seat and are bent inward.
In order to close the clamping ring, which is preferably produced by punching out and bending a sheet-metal strip, the two opposite end portions of the sheet-metal strip can be provided in each case with an opening for the clamping securing bolt and can be placed one above the other with aligned openings in order to guide the clamping securing bolt through the openings and, as a result, to connect the end portions of the sheet-metal strip to each other in this region.
As an alternative, however, provision may also be made for the sheet-metal strip to have just a single opening for the clamping securing bolt and for the ends of the sheet-metal strip to be connected to each other at a distance from the opening, preferably by the two end portions being hooked together in such a manner that, after being securely clamped on the object, they can no longer be detached from each other.